1. Field of the Invention
This invention relates to the manufacture of cellulose fibre by a method comprising the spinning of continuous cellulose filaments from a solution of cellulose in an organic solvent, particularly an amine oxide solvent. Cellulose manufactured in this manner is known as lyocell and will hereafter be referred to as solvent-spun cellulose or lyocell. The invention particularly aims to provide a detection means to enable the presence of damage or any other undesirable matter on the formed continuous filaments after they have been crimped and before they are passed to a cutter to be cut to desired staple fibre length to be detected.
The manufacture of lyocell cellulose filaments is described, for example, in U.S. Pat. No. 4,416,698 the contents of which are incorporated herein by reference. This patent discloses a method of producing cellulose filaments by dissolving the cellulose in a suitable solvent such as a tertiary amine N-oxide.
A hot solution of the cellulose is extruded or spun through a suitable die assembly including a jet to produce filamentary material which is passed into water to leach out the amine oxide solvent from the extruded filaments.
2. Description of the Related Art
The production of artificially formed filaments of material by extruding or spinning a solution or liquid through a spinnerette to form the filaments is, of course, well known. Initially, relatively small numbers of individual filaments were prepared, which filaments were individually wound up for use as continuous filament material. This meant that the number of continuous filaments which needed to be produced was essentially dictated by the number of filaments which could be individually wound either before or after drying.
However, if fibre is produced as a tow or if fibre is produced as a staple fibre then different criteria apply to the number of filaments which can be produced at any one time. A tow essentially comprises a bundle of essentially parallel filaments which are not handled individually. Staple fibre essentially comprises a mass of short lengths of fibre. Staple fibre can be produced by the cutting of dry tow or it can be produced by forming a tow, cutting it while still wet, and drying the cut mass of staple fibre.
Because there is no need to handle individual filaments in the case of a tow product or a staple product, large numbers of filaments can be produced simultaneously.
Natural cellulose fibres have a natural crimp, which is advantageous in providing frictional properties when the fibres are put to use, e.g. directly for non-woven products or for the production of yarns for woven or knitted products. Lyocell, however, does not have an inherently natural crimp and it is desirable, therefore, to apply a crimp to the fibres. This may be done as described in U.S. patent application Ser. No. 08/066,543, now abandoned, entitled "Manufacture of Crimped Solvent-Spun Cellulose Fibre", the contents of which are also incorporated herein by reference. In that application is described a method and apparatus in which a continuous tow of solvent-spun cellulose filaments is formed and is passed to a crimping means comprising a nip leading into a stuffer box in which the filaments are crimped and in which the stuffer box is injected with dry steam during the crimping process. The so-crimped fibres can then be passed to a cutter to be cut to desired staple fibre length.
The present invention aims to provide a means of quality control and of alerting to damage to the crimped filamentary tow after it leaves the stuffer box and before it is passed to the cutter or to storage.